Trade-off between pulse rate and radiation dose during modified barium swallow examination: what is the reality?

AIM: To evaluate the effect of modification of dose mode and frame rate on patient radiation dose during modified barium swallow (MBS) examinations. MATERIALS AND METHODS: A retrospective review was undertaken of consecutive MBS examinations performed over 6 months in the inpatient setting. Patients were divided into two cohorts: pre-implementation of the MBS Impairment Profile (MBSImP; low rate, normal dose) and post-implementation (high rate, low dose). Prior to implementation, pulse rate and dose testing were performed on multiple phantoms. RESULTS: Four hundred and forty-nine patients were included in the pre-implementation cohort and 378 in the post-implementation cohort. Phantom dose testing demonstrated no significant difference in dose on either phantom between low rate/normal dose and high rate/low dose modes. Prior to MBS standardisation, the mean radiation dose was 5.86 (±4.35) mGy. Following standardisation, the mean radiation dose was 4.72 (±3.77) mGy (p<0.0001). The mean fluoroscopy time for MBS prior to standardisation was 83.8 (±44.4) seconds and the mean fluoroscopy time for MBS after standardisation was 82.3 (±39.8) seconds (p=0.62). The dose rate for MBS prior to standardisation was 4.35 (±2.42) and the dose rate for MBS after standardisation was 3.55 (±2.41) mGy/s (p<0.0001). CONCLUSION: Adjustments made to lower the dose mode and the increase in fluoroscopy frame rate decreased the patient radiation dose and did not increase fluoroscopy time.

Future Tail Tales: A Forward-Looking, Integrative Perspective on Tail Research.

Synopsis Tails are a defining characteristic of chordates and show enormous diversity in function and shape. Although chordate tails share a common evolutionary and genetic-developmental origin, tails are extremely versatile in morphology and function. For example, tails can be short or long, thin or thick, and feathered or spiked, and they can be used for propulsion, communication, or balancing, and they mediate in predator-prey outcomes. Depending on the species of animal the tail is attached to, it can have extraordinarily multi-functional purposes. Despite its morphological diversity and broad functional roles, tails have not received similar scientific attention as, for example, the paired appendages such as legs or fins. This forward-looking review article is a first step toward interdisciplinary scientific synthesis in tail research. We discuss the importance of tail research in relation to five topics: (1) evolution and development, (2) regeneration, (3) functional morphology, (4) sensorimotor control, and (5) computational and physical models. Within each of these areas, we highlight areas of research and combinations of long-standing and new experimental approaches to move the field of tail research forward. To best advance a holistic understanding of tail evolution and function, it is imperative to embrace an interdisciplinary approach, re-integrating traditionally siloed fields around discussions on tail-related research.

Adaptation of the WHO guideline for residual DNA in parenteral vaccines produced on continuous cell lines to a limit for oral vaccines.

Although there is a WHO guidance for a limit on residual DNA for parenterally administered vaccines produced on continuous cell lines, there is no corresponding guidance for oral vaccines. To help determine an oral limit, we performed a study of Vero cell DNA uptake in rats, in which the relative uptake and persistence of Vero cell DNA administered orally was compared to its uptake when delivered intramuscularly (IM). The results of this study allowed the generation of an empirically derived IM versus oral factor (10(6)) representing the relative inefficiency of DNA uptake by oral administration. This factor was then applied to the WHO recommended parenteral limit of 10 ng/dose to determine a corresponding upper limit on the level of residual Vero cell DNA for an oral vaccine of 10 mg. As a conservative approach, this empirically determined limit was reduced 100-fold to 100 microg. Thus, the results of this animal study, together with additional evidence in the literature, support a residual DNA safety limit of 100 microg per dose for an oral vaccine produced on a continuous cell line.

Thiosulfate disproportionation by Desulfotomaculum thermobenzoicum.

Desulfotomaculum thermobenzoicum, but not Desulfotomaculum nigrificans, Desulfotomaculum ruminis, or Desulfosporosinus orientis, grew by disproportionation of thiosulfate, forming stoichiometric amounts of sulfate and sulfide; sulfite was not disproportionated. The addition of acetate enhanced growth and thiosulfate disproportionation by D. thermobenzoicum compared to those observed with thiosulfate alone.

An EXAFS study of zinc coordination in microbial cells.

Five microbes were isolated from metal amended enrichment cultures derived from the sediments of a lake contaminated by a zinc smelter. Each of these organisms was grown in pure culture in the presence of zinc. Quick Extended X-ray Absorption Fine Structure (QEXAFS) spectroscopy was used to investigate the average coordination environment of the zinc associated with the microbial biomass. Fitting of the first coordination shell of zinc shows that significant differences exist for each microbial species examined. The coordination environment of zinc varies between sulfurs to six-fold nitrogen/oxygen. with two microbial strains showing mixed coordination shells. Further study is required in order to characterize these sites and their locations within the cell.

Design and evaluation of a tryptophanless RecA protein with wild type activity.

The C-terminal domain of the Escherichia coli RecA protein contains two tryptophan residues whose native fluorescence emission provides an interfering background signal when other fluorophores such as 1,N(6)-ethenoadenine, 2-aminopurine and other tryptophan residues are used to probe the protein's activities. Replacement of the wild type tryptophans with nonfluorescent residues is not trivial because one tryptophan is highly conserved and the C-terminal domain functions in both DNA binding as well as interfilament protein-protein contact. We undertook the task of creating a tryptophanless RecA protein with WT RecA activity by selecting suitable amino acid replacements for Trp290 and Trp308. Mutant proteins were screened in vivo using assays of SOS induction and cell survival following UV irradiation. Based on its activity in these assays, the W290H-W308F W-less RecA was purified for in vitro characterization and functioned like WT RecA in DNA-dependent ATPase and DNA strand exchange assays. Spectrofluorometry indicates that the W290H-W308F RecA protein generates no significant emission when excited with 295-nm light. Based on its ability to function as wild type protein in vivo and in vitro, this dark RecA protein will be useful for future fluorescence experiments.

Syntrophus aciditrophicus sp. nov., a new anaerobic bacterium that degrades fatty acids and benzoate in syntrophic association with hydrogen-using microorganisms.

Strain SBT is a new, strictly anaerobic, gram-negative, nonmotile, non-sporeforming, rod-shaped bacterium that degrades benzoate and certain fatty acids in syntrophic association with hydrogen/formate-using microorganisms. Strain SBT produced approximately 3 mol of acetate and 0.6 mol of methane per mol of benzoate in coculture with Methanospirillum hungatei strain JF1. Saturated fatty acids, some unsaturated fatty acids, and methyl esters of butyrate and hexanoate also supported growth of strain SBT in coculture with Desulfovibrio strain G11. Strain SBT grew in pure culture with crotonate, producing acetate, butyrate, caproate, and hydrogen. The molar growth yield was 17 +/- 1 g cell dry mass per mol of crotonate. Strain SBT did not grow with fumarate, iron(III), polysulfide, or oxyanions of sulfur or nitrogen as electron acceptors with benzoate as the electron donor. The DNA base composition of strain SBT was 43.1 mol% G+C. Analysis of the 16 S rRNA gene sequence placed strain SBT in the delta-subdivision of the Proteobacteria, with sulfate-reducing bacteria. Strain SBT was most closely related to members of the genus Syntrophus. The clear phenotypic and genotypic differences between strain SBT and the two described species in the genus Syntrophus justify the formation of a new species, Syntrophus aciditrophicus.